New Delhi, May 19 - Shattering the myth of big hydropower projects being clean, a new scientific study has revealed that large dams in the country are accountable for at least 19 percent of India's global warming emissions, especially methane.

According to the study, Indian dams are larger methane emitters and total methane emissions from the country's large dams could be around 33.5 million tonnes - per annum, including emissions from reservoirs -, spillways - and turbines of hydropower dams -.

While total generation of methane from India's reservoirs is around 45.8 MT, emission of methane from all the reservoirs of the world remained 120 MT per annum, said the study conducted by Brazil's National Institute for Space Research -.

The difference between the figures of methane generation and emission is due to the oxidation of methane as it rises from the bottom of a reservoir to its surface.

'Large dams in India are responsible for about a fifth of the country's total global warming. These dams are the largest global warming contributors compared to all other nations,' the research noted.

The methane emission from India's dams is estimated at 27.86 percent of the methane emission from all the large dams of the world - more than the share of any other country.

'Brazil comes second with the emission of 21.8 MT per annum, which is 18.13 percent of the global figure,' the study said.

'The Indian government has been blind to this issue so far, even though it has been known for more than a decade now that reservoirs in tropical climate are significant sources of global warming gases,' South Asia Network on Dams, Rivers & People, a network of organisations that works on issues related to water, said in a press release Friday.

'We have constituted various guidelines to help the government in fighting global warming,' the statement said.